Plasma processing apparatus

ABSTRACT

A plasma processing apparatus includes a baffle structure between a mounting table and a processing chamber. The baffle structure has a first member and a second member. The first member has a first cylindrical part extending between the mounting table and the processing chamber, and a plurality of through-holes elongated in the vertical direction is formed in an array in the circumferential direction in the first cylindrical part. The second member has a second cylindrical part having an inner diameter greater than the outer diameter of the cylindrical part for the first member. The second member moves up and down in a region that includes the space between the first member and the processing chamber.

This application is a divisional of U.S. patent application Ser. No.15/312,225 filed Nov. 18, 2016, which is a 35 U.S.C. 371 National PhaseEntry Application from PCT/JP2015/066318, filed Jun. 5, 2015, whichclaims priority to Japanese Patent Application Nos. 2014-126366, filedJun. 19, 2014 and 2015-030444, fried Feb. 19, 2015, the disclosures ofwhich are incorporated herein in their entirety by reference.

FIELD OF THE INVENTION

The disclosure relates to a plasma processing apparatus.

BACKGROUND OF THE INVENTION

In manufacturing electronic devices such as semiconductor devices orFPDs (Flat Panel Displays), a target object is processed by a plasma. Aplasma processing apparatus used for plasma processing generallyincludes a processing chamber, a mounting table, a gas supply unit, anda gas exhaust unit. The mounting table is installed in the processingchamber. The gas supply unit and the gas exhaust unit are connected to aspace in the processing chamber.

Recently, two or more plasma processes need to be performed continuouslyunder different pressure conditions in a single plasma processingapparatus. In the plasma process requiring change of the pressure, apressure changing period, i.e., a transition time, needs to beshortened. Therefore, it is required to reduce a volume of a space wherea processing target object is provided.

A plasma processing apparatus disclosed in Japanese Patent ApplicationPublication No. 2001-196313 is suggested as a plasma processingapparatus that meets the above-described demand. The plasma processingapparatus disclosed in Japanese Patent Application Publication No.2001-196313 includes two baffle plates provided between a mounting tableand a processing chamber. A first space above the two baffle platesincludes a region where the target object is provided. The first spaceis connected to a gas supply unit. A second space below the two baffleplates is connected to a gas exhaust unit.

The two baffle plates are annular plates extending in a horizontaldirection. A plurality of openings is formed in each of the two baffleplates and arranged in a circumferential direction. In the plasmaprocessing apparatus disclosed in Japanese Patent ApplicationPublication No. 2001-196313, an overlapping degree of the openings ofthe two plates in a vertical direction is controlled by rotating one ofthe two baffle plates in the circumferential direction. Accordingly, inthe plasma processing apparatus disclosed in Japanese Patent ApplicationPublication No. 2001-196313, a conductance between the first space andthe second space is controlled and a pressure in the first space iscontrolled.

However, in the plasma processing apparatus disclosed in Japanese PatentApplication Publication No. 2001-196313, it is not possible to set thepressure in the first space to a high level without extremely reducing agap between the two baffle plates. In other words, unless the gapbetween the two baffle plates is extremely reduced, the conductancebetween the first space and the second space cannot be reduced. However,if the gap between the two baffle plates is reduced, the baffle platesare made to be in contact with each other and this may lead togeneration of particles.

Further, in order to allow the contact between the two baffle plates orin order to accurately arrange the two baffle plates such that the gaptherebetween becomes small, the two baffle plates need to have largethicknesses. However, in the case of using the two baffle plates havinglarge thicknesses, even if the two baffle plates are arranged such thatthe openings formed therein are completely overlapped with each other,it is not possible to reduce the pressure in the first space due to asmall conductance between the first space and the second space. In orderto reduce the pressure in the first space, the size of the openingsformed in the two baffle plates needs to be increased. However, if thesize of the openings is increased, a plasma enters the second space.Further, in the case of using the two baffle plates having largethicknesses, a driving unit for the baffle plates is scaled-up in orderto deal with the increase in the weight of the baffle plates. Therefore,it is not practical to increase the thicknesses of the baffle plates andthe size of the openings formed in the baffle plates.

SUMMARY OF THE INVENTION

In view of the above, the disclosure provides a plasma processingapparatus capable of increasing a control range of a pressure in a spacewhere a processing target object is provided.

In accordance with an aspect of the present disclosure, there isprovided a plasma processing apparatus for performing plasma processingon a target object. The plasma processing apparatus includes aprocessing chamber, a mounting table, a baffle structure, a gas supplyunit, and a driving unit. The mounting table is provided in theprocessing chamber and the mounting table has a mounting region on whicha target object is mounted. The baffle structure provided below themounting region and between the mounting table and the processingchamber. The baffle structure defines a first space including themounting region and a second space below the mounting region in theprocessing chamber. The baffle structure includes a first member and asecond member. The first member has a first cylindrical part extendingbetween the mounting table and the processing chamber and having aplurality of through-holes elongated in a vertical direction andarranged in a circumferential direction. The second member has a secondcylindrical part having an inner diameter greater than an outer diameterof the first cylindrical part. The gas supply unit is connected to thefirst space. A gas exhaust unit is connected to the second space. Thedriving unit is configured to vertically move the second cylindricalpart in a region including a gap between the first member and theprocessing chamber.

In this plasma processing apparatus, it is possible to control a ratioin which the through-holes are shielded with respect to the second spaceby the second cylindrical part by controlling a vertical positionalrelationship between the first cylindrical part of the first member andthe second cylindrical part of the second member. Accordingly, theconductance between the first space and the second space can becontrolled. In a state where the second cylindrical part faces theentire through-holes, the conductance between the first space and thesecond space is mainly determined by the conductance of the gap betweenthe two cylindrical parts. Therefore, a small conductance between thefirst space and the second space can be obtained regardless of thelength in a diametrical direction of the gap between the firstcylindrical part of the first member and the second cylindrical part ofthe second member, i.e., without requiring a high accuracy for the gap.In a state where the second cylindrical part does not face thethrough-holes, a large conductance between the first space and thesecond space can be obtained. Accordingly, in the plasma processingapparatus, it is possible to increase a control range of a pressure inthe first space where the wafer is disposed.

Although the pressure is applied to the first member and the secondmember in the diametrical direction, the first member and the secondmember are hardly bent by the pressure due to the cylindrical shapethereof. Therefore, even if the second member is moved, the firstcylindrical part and the second cylindrical part are hardly brought intocontact with each other and, thus, generation of particles can besuppressed. Further, the second member can be moved at a high speed dueto its thin thickness. Since the through-holes are arranged in thecircumferential direction, non-uniformity of a gas exhaust amount in thecircumferential direction can be reduced.

The plasma processing apparatus may further include a control unitconfigured to control the driving unit. The control unit may performfirst control in which the driving unit is controlled to set a verticalposition of the second member to a first position, and second control inwhich the driving unit is controlled to set the vertical position of thesecond member to a second position different from the first position. Inthe plasma processing, a pressure in the first space in a second controlcan set differently from a pressure in the first space in the firstcontrol. Therefore, after processing a target object by the plasmaprocessing apparatus in one of a low pressure and a high pressure, thetarget object can be processed in the other of the low pressure and thehigh pressure in the same plasma apparatus. Thereby, it is possible toprocess the target object in the same plasma processing apparatus whilechanging the pressure.

The control unit may control the gas supply unit to supply a first gasduring the first control and to supply a second gas different from thefirst gas during the second control. With this configuration, it ispossible to process a target object using the same plasma processingapparatus while changing gas species and a pressure.

EFFECT OF THE INVENTION

As described above, there is provided a plasma processing apparatuscapable of increasing a control range of a pressure in a space where thetarget object is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a plasma processing apparatus according to anembodiment.

FIGS. 2 and 3 are perspective views schematically showing a firstcylindrical part of a first member and a second cylindrical part of asecond member of a baffle structure according to an embodiment.

FIGS. 4 and 5 are broken perspective views showing the first member andthe second member of the baffle structure according to the embodiment.

FIG. 6 is an enlarged cross sectional view showing a part of the firstcylindrical part of the first member and a part of the secondcylindrical part of the second member of the baffle structure accordingto the embodiment.

FIG. 7 is a cross sectional view showing examples of the first member,the second member and a shaft body.

FIG. 8 is a perspective view schematically showing an example of amechanism for vertically moving the second member.

FIG. 9 shows an embodiment of a control system related to the bafflestructure.

FIG. 10 explains a comparative simulation 1.

FIG. 11 shows a result of the comparative simulation 1.

FIG. 12 shows results of a simulation 2 and a comparative simulation 2.

FIG. 13 is a graph showing results of a test example 1 and a comparativeexample 1.

FIG. 14 is a graph showing results of a test example 2 and a comparativeexample 2.

FIG. 15 is a graph showing results of a test example 3 and a comparativeexample 3.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments will be described in detail with reference tothe accompanying drawings. Like reference numerals will be used for likeor corresponding parts throughout the respective drawings.

FIG. 1 schematically shows a plasma processing apparatus according to anembodiment. In FIG. 1 , a vertical cross sectional structure of a plasmaprocessing apparatus 10 is schematically illustrated. The plasmaprocessing apparatus 10 shown in FIG. 1 is a capacitively coupledparallel plate type plasma etching apparatus. The plasma processingapparatus 10 includes a processing chamber 12. The processing chamber 12is made of, e.g., anodically oxidized aluminum. The processing chamber12 has a sidewall 12 s. The sidewall 12 s has a substantiallycylindrical shape. A central axis line of the sidewall 12 ssubstantially coincides with an axis line 2 extending in a verticaldirection. An opening 12 g through which a wafer W is loaded or unloadedis formed at the sidewall 12 s. The opening 12 g can be opened andclosed by a gate valve 52.

A mounting table 14 is provided in the processing chamber 12. In oneembodiment, the mounting table 14 is supported by a supporting portion16. The supporting portion 16 is a substantially cylindrical insulatingmember extending upward from a bottom portion of the processing chamber12. In one embodiment, the supporting portion 16 supports the mountingtable 14 while being in contact with a lower peripheral portion of themounting table 14.

The mounting table 14 includes a lower electrode 18 and an electrostaticchuck 20. The lower electrode 18 has a substantially disc shape and ismade of a conductor. The lower electrode 18 is connected to a first highfrequency power supply (HFS) via a matching unit MU1. The first HFSgenerates a high frequency power for plasma generation which has afrequency in a range from 27 MHz to 100 MHz, e.g., 40 MHz in thisexample. The matching unit MU1 includes a circuit for matching an outputimpedance of the first HFS and an input impedance of the load side (thelower electrode 18 side).

The lower electrode 18 is also connected to a second high frequencypower supply (LFS) via a matching unit MU2. The second LFS generates ahigh frequency power for ion attraction (high frequency bias power) andsupplies the high frequency bias power to the lower electrode 18. Thehigh frequency bias power has a frequency in a range from 400 kHz to13.56 MHz, e.g., 3 MHz in this example. The matching unit MU2 includes acircuit for matching an output impedance of the second LFS and the inputimpedance of the load side (the lower electrode 18 side).

The electrostatic chuck 20 is provided on the lower electrode 18. Theelectrostatic chuck 20 has a structure in which an electrode 20 a madeof a conductive film is embedded between two insulating layers or twoinsulating sheets. A DC power supply 22 is electrically connected to theelectrode 20 a via a switch SW. A top surface of the electrostatic chuck20 serves as a mounting region 20 r on which the wafer W as a processingtarget object is mounted. When a DC voltage from the DC power supply 22is applied to the electrode 20 a of the electrostatic chuck 20, thewafer W mounted on the mounting region 20 r is attracted and held on theelectrostatic chuck 20 by an electrostatic force such as a Coulomb forceor the like.

In the plasma processing apparatus 10, a focus ring FR is provided tosurround an edge of the wafer W. The focus ring FR may be made of, e.g.,silicon or quartz.

A flow path 18 a is formed in the lower electrode 18. A coolant, e.g.,cooling water, is supplied to the flow path 18 a from an externalchiller unit through a line 26 a. The coolant flowing in the flow path18 a returns to the chiller unit, through a line 26 b. A temperature ofthe wafer W mounted on the electrostatic chuck 20 is controlled bycontrolling a temperature of the coolant.

A gas supply line 28 is formed in the mounting table 14. The gas supplyline 28 supplies a heat transfer gas, e.g., He gas, from a heat,transfer gas supply unit to a gap between the top surface of theelectrostatic chuck 20 and a backside of the wafer W.

The plasma processing apparatus 10 further includes an upper electrode30. The upper electrode 30 is provided above the lower electrode 18 toface the lower electrode 18. The lower electrode 18 and the upperelectrode 30 are approximately parallel to each other.

The upper electrode 30 is held at a ceiling portion of the processingchamber 12 through an insulating shield member 32. The upper electrode30 may include an electrode plate 34 and an electrode holder 36. Theelectrode plate 34 is in contact with a space in the processing chamber12 and has a plurality of gas injection openings 34 a. The electrodeplate 34 may be made of a semiconductor or a low-resistance conductorhaving low Joule's heat.

The electrode holder 36 detachably holds the electrode plate 34 and ismade of a conductive material, e.g., aluminum. The electrode holder 36has a water-cooling structure. A gas diffusion space 36 a is provided inthe electrode holder 36. A plurality of gas holes 36 b communicatingwith the gas injection openings 34 a extends downward from the gasdiffusion space 36 a. Further, the electrode holder 36 includes a gasinlet port 36 c for guiding a processing gas into the gas diffusionspace 36 a. A gas supply line 38 is connected to the gas inlet port 36c.

A gas source group 40 is connected to the gas supply line 38 through avalve group 42 and a flow rate controller group 44. The gas source group40 includes a plurality of different gas sources. The valve group 42includes a plurality of valves. The flow rate controller group 44includes a plurality of flow rate controllers such as mass flowcontrollers. The gas sources of the gas source group 40 are connected tothe gas supply line 38 via corresponding valves of the valve group 42and corresponding flow rate controllers of the flow rate controllergroup 44.

In the plasma processing apparatus 10, a gas from at least one gassource selected among a plurality of gas sources of the gas source group40 is supplied at a controlled flow rate to the gas supply line 38through a corresponding flow rate controller and a corresponding valve.The gas supplied to the gas supply line 38 reaches the gas diffusionspace 36 a and then is guided to the space in the processing chamber 12through the gas holes 36 b and the gas injection openings 34 a. The gassource group 40, the flow rate controller group 44, the valve group 42,the gas supply line 33, and the upper electrode 30 constitute a gassupply unit GS according to an embodiment. The gas supply unit GS isconnected to a first space S1 to be described later.

As shown in FIG. 1 , a gas exhaust line 48 is connected to the bottomportion of the processing chamber 12. A gas exhaust unit 50 is connectedto the gas exhaust line 48. Accordingly, the gas exhaust unit 50 isconnected to a second space S2 to be described later. The gas exhaustunit 50 includes a vacuum pump such as a turbo molecular pump.

The plasma processing apparatus 10 further includes a control unit Cnt.The control unit Cnt is a computer including a processor, a storageunit, an input device, a display device and the like. The control unitCnt controls the respective components of the plasma processingapparatus 10. The control unit Cnt can allow an operator to inputcommands to manage the plasma processing apparatus 10 by using the inputdevice. The control unit Cnt can display the operation state of theplasma processing apparatus 10 on the display device. The storage unitof the control unit Cnt stores therein a control program for controllingvarious processes performed in the plasma processing apparatus 10, and aprogram, i.e., a processing recipe, for performing processes of therespective components of the plasma processing apparatus 10 based on theprocessing conditions.

In the plasma processing apparatus 10, in order to process the wafer W,a gas is supplied from at least one gas source selected among theplurality of gas sources of the gas source group 40 into the processingchamber 12. Further, a high frequency electric field is generatedbetween the lower electrode 18 and the upper electrode 30 by applyingthe high frequency power for plasma generation to the lower electrode18. A plasma of the gas supplied into the processing chamber 12 isgenerated by the high frequency electric field thus generated. The waferW is processed, e.g., etched, by the plasma thus generated. Further,ions may be attracted to the wafer W by applying the high frequency biaspower to the lower electrode 18.

As shown in FIG. 1 , the plasma processing apparatus 10 further includesa baffle structure 60. The baffle structure 60 is provided at a locationbelow the mounting region 20 r and between the mounting table 14 and thesidewall 12 s of the processing chamber 12. The baffle structure 60defines the first space S1 and the second space S2 in the processingchamber 12. The first space S1 includes the mounting region 20 r onwhich the wafer W is mounted. The second space S2 is located below themounting region 20 r. The gas supply unit GS is connected to the firstspace S1. The gas exhaust unit 50 is connected to the second space S2.

Hereinafter, FIGS. 2 to 6 as well as FIG. 1 will be referred to. FIGS. 2and 3 are perspective views schematically showing a first cylindricalpart of a first member and a second cylindrical part of a second memberof the baffle structure according to an embodiment. FIGS. 4 and 5 arepartial perspective views showing the first member and the second memberof the baffle structure according to the embodiment. FIG. 6 is anenlarged cross sectional view showing a part of the first cylindricalpart of the first member and a part of the second cylindrical part ofthe second member of the baffle structure according to the embodiment.FIGS. 2 and 3 are perspective views used for better description. Theillustrated sizes of the first and the second cylindrical part, theillustrated size and the illustrated number of through-holes formed inthe first cylindrical part are different from the actual sizes of thefirst and the second cylindrical part, the actual size and the actualnumber of the through-holes formed in the first cylindrical part.

As shown in FIGS. 1, 4 and 5 , the baffle structure 60 includes a firstmember 61 and a second member 62. The first member 61 is formed bycoating Y₂O₃ on a surface of a metal such as aluminum or stainlesssteel. The first member 61 includes a first cylindrical part 61 a, alower annular part 61 b, and an upper annular part 61 c.

As shown in FIGS. 1 to 5 , the first cylindrical part 61 a has asubstantially cylindrical shape and a central axis line thereofsubstantially coincides with an axis line Z. A thickness of the firstcylindrical part 61 a is, e.g., 5 mm. An outer diameter of the firstcylindrical part 61 a is, e.g., 550 mm. As shown in FIG. 1 , the first,cylindrical part 61 a extends between the mounting table 14 and thesidewall 12 s of the processing chamber 12.

As shown in FIGS. 1 to 5 , the first cylindrical part 61 a has aplurality of through-holes 61 h. The through-holes 61 h penetratethrough the first cylindrical part 61 a in a radial direction (i.e., ina diametrical direction) with respect to the axis line Z. Thethrough-holes 61 h have a long slit shape in a vertical direction. Thethrough-holes 61 h are distributed in the entire circumference of thefirst cylindrical part 61 a while being arranged at a substantiallyregular pitch in a circumferential direction with respect to the axisline Z.

A width of each of the through-holes 61 h, i.e., a width in a directionperpendicular to the vertical direction of each of the through-holes 61h, may be about 3.5 mm or less in view of suppressing leakage of aplasma into the second space S2. A length in the vertical direction ofeach of the through-holes 61 b may be set depending on a control rangeof a pressure in the first space S1. For example, the length in thevertical direction of each of the through-holes 61 h is 30 mm.

As shown in FIGS. 1, 4 and 5 , the lower annular part 61 b has anannular shape. The lower annular part 61 b extends from a lower end ofthe first cylindrical part 61 a in a diametrically inward direction. Theupper annular part 61 c has an annular, shape. The upper annular, part61 c extends from an upper end of the first cylindrical part 61 a in adiametrically outward direction. The first member 61 may include thefirst cylindrical part 61 a, the lower annular part 61 b and the upperannular part 61 c which are separate members. In other words, the firstmember 61 may have a separated structure and may be formed by assemblingthe first cylindrical part 61 a, the lower annular part 61 b and theupper annular part 61 c. Or, the first member 61 may be obtained byforming the first cylindrical part 61 a, the lower annular part 61 b andthe upper annular part 61 c as one unit.

As shown in FIG. 1 , the bottom portion 12 b of the processing chamber12 includes a substantially cylindrical supporting portion 12 m. Acylindrical member 64 is provided above the supporting portion 12 m. Thecylindrical member 64 may be made of an insulator, e.g., ceramic. Thecylindrical member 64 extends along an outer peripheral surface of thesupporting portion 16. An annular member 66 is provided on thecylindrical member 64 and the supporting portion 16. The annular member66 extends to a vicinity of an edge of the electrostatic chuck 20 alonga top surface of the lower electrode 18. The aforementioned focus ringFR is installed on the annular member 66.

An inner edge of the lower annular portion 61 b of the first member 61is disposed between the supporting portion 12 m and the cylindricalmember 64. The supporting portion 12 m and the cylindrical member 64 arefixed to each other by, screws. Accordingly, the inner peripheralportion of the lower annular portion 61 b is interposed between thesupporting portion 12 m and the cylindrical member 64.

The sidewall 12 s of the processing chamber 12 includes an upper part 12s 1 and a lower part 12 s 2. The plasma processing apparatus 10 furtherincludes a supporting member 68. The supporting member 68 has asubstantially annular upper part 68 a and a substantially annular lowerpart 68 c. The upper part 68 a and the lower part 68 c are connected viaa substantially cylindrical intermediate part. The upper part 68 a ofthe supporting member 68 is interposed between the upper part 12 s 1 andthe lower part 12 s 2 of the sidewall 12 s. The lower part 68 c of thesupporting member 68 extends in a diametrically inward direction insidethe processing chamber 12. The upper annular part 61 c of the firstmember 61 is fixed to the lower part 68 c of the supporting member 68.The upper annular part 61 c of the first member 61 is fixed to the lowerpart 68 c of the supporting member 68 by, e.g., screws. The supportingmember 68 may include the upper part 68 a, the intermediate part, andthe lower part 68 c which are separate members. In other words, thesupporting member 68 may have a separated structure and may be formed byassembling the upper part 68 a, the intermediate part and the lower part68 c. Or, the supporting member 68 may be obtained by forming the upperpart 68 a, the intermediate part and the lower part 68 c as one unit.

The second member 62 may be formed by coating Y₂O₃ on a surface of ametal, e.g., aluminum or stainless steel. As shown in FIGS. 1, 4 and 5 ,the second member 62 includes a second cylindrical part 62 a and anannular part 62 b. As shown in FIGS. 1 to 5 , the second cylindricalpart 62 a has a substantially cylindrical shape and a central axis linethereof substantially coincides with the axis line Z. Further, thesecond cylindrical part 62 a has an inner diameter greater than theouter diameter of the first cylindrical part 61 a. For example, theinner diameter of the second cylindrical part 62 a is 550.4 mm, and thethickness of the second cylindrical part 62 a is 5 mm.

As shown in FIGS. 1, 4 and 5 , the annular part 62 b of the secondmember 62 has a substantially annular shape. In one embodiment, theannular part 62 b extends from the lower end of the second cylindricalpart 62 a in a diametrically outward direction. The second member 62 mayinclude the second cylindrical part 62 a and the annular part 62 b whichare separate members. In other words, the second member 62 may have aseparated structure and may be formed by assembling the secondcylindrical part 62 a and the annular part 62 b. Or, the second member62 may be obtained by forming the second cylindrical part 62 a and theannular part 62 b as one unit. As shown in FIG. 1 , the annular part 62b of the second member 62 is connected to a shaft body 69. In oneembodiment, the shaft body 69 is a feed screw. The annular part 62 b isconnected to the shaft body 69 via a nut. Further, the shaft body 69 isconnected to a driving unit 70. The driving unit 70 is, e.g., a motor.The driving unit 70 vertically moves the second member 62 along theshaft body 69. Accordingly, the second cylindrical part 62 a of thesecond member 62 is vertically moved in a region including a gap betweenthe first cylindrical part 61 a of the first member 61 and the sidewall12 s of the processing chamber 12. Although only one shaft body 69 isillustrated in FIG. 1 , a plurality of shaft bodies arranged in acircumferential direction may be connected to the annular part 62 b ofthe second member 62.

Hereinafter, FIGS. 7 and 6 will be referred to FIG. 7 is a crosssectional view showing examples of the first member, the second member,and the shaft body. FIG. 8 is a perspective view schematically showingan example of a mechanism for vertically moving the second member.Hereinafter, the example of the mechanism for vertically moving thesecond member will be described with reference to FIGS. 7 and 8 . InFIG. 6 , components such as connectors C1 and C2 to be described laterare not illustrated.

As shown in FIG. 7 , the shaft body 69 includes a screw part 69 a, ashaft 69 b, the connector C1, and the connector C2. The shaft 69 b has asubstantially columnar shape and extends in a vertical direction. Anupper end of the shaft 69 b is positioned inside the processing chamber12, and a lower end of the shaft 69 b is positioned outside theprocessing chamber 12 while penetrating through the bottom portion 12 bof the processing chamber 12. The lower end of the shaft 69 b isconnected to a rotational driving axis 70 a of the driving unit 70(e.g., a motor) via the connector C1. A sealing unit SL such as magneticfluid seal is provided between the shaft 69 b and the bottom portion 12b of the processing chamber 12.

The upper end of the shaft 69 b is connected to a lower end of the screwpart 69 a via the connector C2. The screw part 69 a extends in avertical direction above the shaft 69 b. A nut 62 n to be screw-coupledto the screw part 69 a is attached to the annular part 62 b of thesecond member 62. When the shaft body 69 is rotated by the driving unit70, the rotation of the shaft body 69 is converted to vertical movementof the second member 62. Therefore, a mechanism illustrated in FIG. 7can vertically move the second member 62.

The screw part 69 a, the shaft 69 b, and the connector C2, and the nut62 n which form the shaft body 69 shown in FIG. 7 is provided inside theprocessing chamber 12. Therefore, all or at least one of the shaft 69 b,and the connector C2, and the nut 62 n may be made of an insulator. Or,only the screw part 69 a that is a component located at a positionclosest to the first space S1 where the plasma is generated may be madeof an insulator.

In one example, one or more shaft bodies 80 may be provided in additionto the shaft body 69 as shown in FIG. 8 . The shaft body 80 has asubstantially columnar shape and extends in a vertical direction througha through-hole formed in the annular part 62 b of the second member 62.A bearing may be provided between the shaft body 80 and the annular part62 b of the second member 62. A lower end of the shaft 80 may be fixedto the bottom portion 12 b of the processing chamber 12 and an upper endof the shaft 80 may be fixed to the supporting member 68. The shaftbodies 80 and the shaft body 69 are arranged in the circumferentialdirection with respect to the axis line Z. For example, the shaft body69 and three shaft bodies 80 (two shaft bodies 80 are illustrated inFIG. 8 ) may be arranged in the circumferential direction while beingspaced apart from each other at an angle of 90°. By providing the shaft69 and one or more shaft bodies 80, the vertical movement of the secondmember 62 can be realized with high accuracy. The number of the shaftbodies 80 is not limited to three. A plurality of mechanisms, eachincluding the shaft body 69, the connector C1, the connector C2, thesealing unit SL, and the driving unit 70, may be arranged in thecircumferential direction.

As shown in FIGS. 2 and 4 , in the plasma processing apparatus 10, whenthe second cylindrical part 62 a is moved downward, the through-holes 61h formed in the first cylindrical part 61 a are made to directlycommunicate with the second space S2 without facing the secondcylindrical part 62 a, i.e., without being shielded by the secondcylindrical part 62 a. In other words, the first space S1 communicateswith the second space S2 only through the through-holes 61 h. In thatstate, a conductance of a gas channel between the first space S1 and thesecond space S2 is increased. Therefore, a pressure in the first spaceS1 becomes close to a pressure in the second space S2, and the pressurein the first space S1 can be set to a low level.

As shown in FIGS. 3, 5 and 6 , when the second cylindrical part 62 a ismoved upward and made to face the through-holes 61 h, i.e., when thethrough-holes 61 h are shielded by the second cylindrical part 62 a, thefirst space S1 communicates with the second space S2 via thethrough-holes 61 h and a gap GP (see FIG. 6 ) between the firstcylindrical part 61 a and the second cylindrical part 62 a. In thatstate, the conductance of the gas channel between the first space S1 andthe second space S2 is decreased. Therefore, a difference between thepressure in the first space S1 and the pressure in the second space S2is increased and the pressure in the first space S1 can be set to a highlevel. A length GW in a diametrical direction of the gap GP between thefirst cylindrical part 61 a and the second cylindrical part 62 a may beset to, e.g., 0.4 mm.

FIG. 9 shows an embodiment of a control system related to the bafflestructure. As shown in FIG. 9 , the driving unit 70 can be controlled bythe control unit Cnt. The control unit Cnt receives signals from adisplacement gauge 90, a pressure gauge 92, and a pressure gauge 94. Thedisplacement gauge 90 measures a vertical position of the second member62 or a distance from a reference position and sends a signal indicatingthe measurement result to the control unit Cnt. The pressure gauge 92measures a pressure in the first space S1 and sends a signal indicatingthe measurement result to the control unit Cnt. The pressure gauge 94measures a pressure in the second space S2 and sends a signal indicatingthe measurement result to the control unit Cnt. The control unit Cntreceives the pressure in the first space S1 which is specified by arecipe, the signal indicating the measurement result of the displacementgauge 90, the signal indicating the measurement result of the pressuregauge 92, and the signal indicating the measurement result of thepressure gauge 94, sends a signal to the driving unit 70, and controlsthe vertical position of the second member 62 by using the driving unit70 such that the pressure in the first space S1 becomes the pressurespecified by the recipe.

In this plasma processing apparatus 10, it is possible to control aratio in which the through-holes 61 h are shielded with respect to thesecond space 32 by the second cylindrical part 62 a by controlling avertical positional relationship between the first cylindrical part 61 aof the first member 61 and the second cylindrical part 62 a of thesecond member 62. Accordingly, the conductance between the first, spaceS1 and the second space S2 can be controlled.

In a state where the second cylindrical part 62 a faces the entirethrough-holes 61 h, the conductance between the first space S1 and thesecond space S2 is mainly determined by the conductance of the gap GPbetween the two cylindrical parts. Therefore, a small conductancebetween the first space S1 and the second space S2 can be obtainedregardless of the length in a diametrical direction of the gap GPbetween the first cylindrical part 61 a of the first member 61 and thesecond cylindrical part 62 a of the second member 62, i.e., withoutrequiring a high accuracy for the gap GP. In a state where the secondcylindrical part 62 a does not face the through-holes 61 h, a largeconductance between the first space S1 and the second space S2 can beobtained. Accordingly, in the plasma processing apparatus 10, it ispossible to increase a control range of a pressure in the first space S1where the wafer W is disposed.

Although the pressure is applied to the first member 61 and the secondmember 62 in the diametrical direction, the first member 61 and thesecond member 62 are hardly bent by the pressure due to the cylindricalshape thereof. Therefore, even if the second member 62 is moved, thefirst cylindrical part 61 a and the second cylindrical part 62 a arehardly brought into contact with each other and, thus, generation ofparticles can be suppressed. Further, the second member 62 can be movedat a high speed due to its thin thickness. Since the through-holes 1 hare arranged in the circumferential direction, non-uniformity of a gasexhaust amount in the circumferential direction can be reduced.

In the plasma processing apparatus 10, an exemplary plasma processing tobe described later can be performed. In a first exemplary plasmaprocessing, the control unit Cnt performs first control and secondcontrol. In the first, control, the control unit Cnt controls thedriving unit 70 such that the vertical position of the second member 62is set to a first position. In the second control, the control unit Cntcontrols the driving unit 70 such that, the vertical position of thesecond member 62 is set to a second position different from the firstposition. The first position may be positioned above the second positionor below the second position. In the first exemplary plasma processing,the wafer W can be processed in the first space S1 by moving the secondmember 62 to the first position during the first control to set thepressure in the first space S1 to one of a high level and a low level.Further, the wafer W can be processed in the first space S1 by movingthe second member 62 to the second position during the second control toset the pressure in the first space S1 to the other one of the highlevel and the low level. The first control and the second control may berepeated alternately.

In a second exemplary plasma processing, the control unit Cnt supplies afirst gas to the gas supply unit GS during the first control andsupplies a second gas to the gas supply unit GS during the secondcontrol. The second gas is different from the first gas. In other words,the second gas has a different composition from that of the first gas.In the second exemplary plasma processing, the first control and thesecond control may be repeated alternately.

In the second exemplary plasma processing, a deposition gas is used asthe first gas and a corrosion gas is used as the second gas and, thus, aprocess of depositing a protective film on the wafer W and a process ofetching a film of the wafer W can be performed alternately. In thisplasma processing, a pressure set as the pressure in the first space S1in the deposition process is different from a pressure set as thepressure in the first space S1 in the etching process. By performing thefirst control and the second control alternately, the plasma processingcan be performed in the same plasma processing apparatus 10. In theplasma processing apparatus 10, it is possible to shorten a transitiontime required to change a pressure in the first space S1 between thedeposition process and the etching process.

The second exemplary plasma processing can also be used for continuouslyetching two different films of the wafer W. In the case of etching twodifferent films, a type of a gas and a pressure in the first space S1which are used for etching one of the films are different from a type ofa gas and a pressure in the first space S1 which are used for etchingthe other film. Therefore, by alternately performing the first controland the second control, such a plasma processing can be performed in thesame plasma processing apparatus 10. Further, in the plasma processingapparatus 10, it is possible to shorten the transition time for changinga pressure in the first space S1 which is required to switch the etchingof one film to the etching of the other film.

While the embodiment has been described, the present disclosure may bevariously modified without being limited to the above-describedembodiment. For example, the shape of the through-holes 61 h formed inthe first cylindrical part 61 a may vary as long as it is verticallylong. For example, the through-holes 61 h may have an inverted triangleshape whose width becomes narrow in a downward direction. Or, thethrough-holes 61 h may have a ridge shape.

The moving speed of the second member 62 by the driving unit 70 may beconstant or may be changed nonlinearly. Accordingly, the pressure in thefirst space S1 can be changed linearly or nonlinearly during themovement of the second member 62.

In the above-described embodiment, the driving unit 70 is a motor andmoves the second member 62 by driving the shaft body 69 that is a feedscrew. However, the driving unit 70 may be a hydraulic or a pneumaticcylinder for vertically moving the second member 62.

In the plasma processing apparatus 10 of the above-described embodiment,the first high frequency power supply HFS is electrically connected tothe lower electrode 18. However, the first high frequency power supplyHFS may be electrically connected to the upper electrode 30.

The plasma processing apparatus 10 of the above-described embodiment isa capacitively coupled plasma processing apparatus. However, the plasmaprocessing apparatus to which the idea disclosed in the above embodimentis applicable may be any plasma processing apparatus, e.g., aninductively coupled plasma processing apparatus, or a plasma processingapparatus using a surface wave such as a microwave.

Hereinafter, simulations and test examples that have been performed tocheck the plasma processing apparatus 10 will be described.

Simulation 3 and Comparative Simulation 1

In simulation 1, a pressure in the first space S1 and a pressure in thesecond space S2 were calculated under the following conditions. In thefollowing, “shielded state” indicates a state in which the secondcylindrical part 62 a faces the entire through-holes 61 h and thethrough-holes 61 h are shielded by the second cylindrical part 62 a.

Conditions of Simulation 1

outer diameter of the first cylindrical part 61 a: 550 mm

thickness of the first cylindrical part 61 a: 5 mm

width of the through-hole 61 h: 3.5 mm

length of the through-hole 61 b: 30 mm

thickness of the second cylindrical part 62 a: 5 mm

inner diameter of the second cylindrical part 62 a: 550.4 mm

gas supply by the gas supply unit GS: N₂ gas (200 sccm)

state of the through-hole 61 h: shielded state

As a result of the simulation 1, a pressure in the first space S1 was420 mTorr (5.6×10¹ Pa) and a pressure in the second space S2 was 19.5mTorr (2.6 Pa). Therefore, in the plasma processing apparatus 10, it ispossible to increase the difference between the pressure in the firstspace S1 and the pressure in the second space S2. As a result, thepressure in the first space S1 can be set to a high level.

A comparative simulation 1 to be described below was performed forcomparison. In the comparative simulation 1, in the baffle structure 60of the plasma processing apparatus 10, annular baffle plates 101 and 102extending in a horizontal direction were provided between the mountingtable 14 and the sidewall 12 s of the processing chamber 12. In thecomparative simulation 1, the baffle plates 101 and 102 were arranged ina vertical direction. FIG. 10 explains the comparative simulation 1. Thecircumferential direction corresponds to the horizontal direction inFIG. 10 . In FIG. 10 , the baffle plates 101 and 102 are illustrated.

In the comparative simulation 1, the thickness of each of the baffleplates 101 and 102 was set to 3.5 mm. In the baffle plate 101 disposedabove the baffle plate 102, 3000 through-holes 101 h, each having adiameter of 3.5 mm, were formed, and 200 pairs of through-hale groups,each including 15 through-holes 101 h arranged in a diametricaldirection, were uniformly arranged in the circumferential direction. Inthe baffle plate 102, 200 through-holes 102 h, each having an elongatedhole shape in the diametrical direction, were arranged at a uniformpitch along the circumferential direction. A diametrical length of thethrough-hole 102 h was set to 60 mm, and a width of the through-hole 102h was set to 3.5 mm. A pressure in the first space S1 was calculatedwhile varying a flow rate of gas in the case of setting a length L ofthe gap between the baffle plates 101 and the baffle plate 102 to 0.1 mmand in the case of setting the length L of the gap between the baffleplates 101 and the baffle plate 102 to 0.6 mm.

FIG. 11 shows a result of the comparative simulation 1. In FIG. 11 , thehorizontal axis represents a flow rate of N₂ gas and the vertical axisrepresents a pressure in the first space S1. Further, in FIG. 11 ,“shielded state” shows a state in which the through-holes 101 h of thebaffle plate 101 and the through-holes 102 h of the baffle plate 102 donot face each other as shown in FIG. 10 , and “open state” indicates astate in which the through-holes 102 h of the baffle plate 102 face theentire through-holes 101 h of the baffle plate 101. In FIG. 11 , anotation L indicates a length of the gap between the baffle plate 101and the baffle plate 102.

As shown in FIG. 11 , when the length L of the gap between the baffleplate 101 and the baffle plate 102 was 0.6 mm, the pressure in the firstspace S1 was increased only up to about 70 mTorr (9.333 Pa) even bysupplying a large amount of N₂ gas in the shielded state. When thelength L of the gap between the baffle plate 101 find the baffle plate102 was 0.1 mm, the pressure in the first space S1 was increased up toabout 130 mTorr (17.33 Pa) by supplying a large amount of N₂ gas in theshielded state. However, even when the length L of the gap between thebaffle plate 101 and the baffle plate 102 was 0.1 mm, the pressure inthe first space S1 was considerably lower than the pressure in the firstspace S1 which was obtained in the simulation 1 of the plasma processingapparatus 10. If the length L of the gap between the baffle plate 101and the baffle plate 102 is set to 0.1 mm, the baffle plates 101 and 102are brought into contact with each other, which is not practical. Fromthe above, the superiority of the plasma processing apparatus 10 hasbeen confirmed.

Simulation 2 and Comparative Simulation 2

In a simulation 2, in the plasma processing apparatus 10 including thebaffle structure 60 having the first, and the second cylindrical part 61a and 62 a having the same sizes as those set in the simulation 1, again G was obtained in the case of supplying N₂ gas of 50 sccm into theprocessing chamber 12 and setting a frequency for alternately switchingthe open state and the shielded state (hereinafter, simply referred toas “frequency”) to various levels. The “open state” is a state in whichthe through-holes 61 h do not face the second cylindrical part 62 a. The“gain G” is defined in the following Eq. (1). In the following Eq. (1),ΔP indicates a difference between a pressure in the first space S1 inthe shielded state and a pressure in the first space S1 in the openstate, and “maximum pressure difference” indicates a maximum pressuredifference in the first space S1 which is realized by the verticalmovement of the second member 62 in the case of supplying N₂ gas of 50sccm into the processing chamber 12.G=log₂₀(ΔP/(maximum pressure difference))  Eq. (1)

A comparative simulation 2 was performed for comparison with thesimulation 2. In the comparative simulation 2, in a plasma processingapparatus different from the plasma processing apparatus 10 in that anannular baffle plate was provided between the sidewall 12 s of theprocessing chamber 12 and the mounting table 14 instead of the bafflestructure 60, a gain G was obtained while setting a frequency foralternately switching the shielded state and the open state to variouslevels by controlling an opening degree of the pressure control valve ofthe gas exhaust unit 50. In the comparative simulation 2, an innerdiameter of the baffle plate was set to 400 mm; an outer diameter of thebaffle plate was set to 520 mm; and a thickness of the baffle plate wasset to 6 mm. As for the baffle plate, an annular plate having uniformlydistributed 6000 through-holes, each having a diameter of 3 mm, wasused. In the comparative simulation 2, a state in which the openingdegree of the pressure control valve of the gas exhaust unit 50 wasminimum was set to the shielded state and a state in which the openingdegree of the pressure control valve of the gas exhaust unit 50 wasmaximum was set to the open state.

FIG. 12 shows the results of the simulation 2 and the comparativesimulation 2. In FIG. 12 , the horizontal axis represents a frequencyfor switching the open state and the shielded state, and the verticalaxis represents the gain G. As shown in FIG. 12 , the amount of decreasein the gain caused by the increase of the frequency was greater in thesimulation 2 in which the open state and the shielded state werealternately switched by the baffle structure 60 chars in the comparativesimulation 2 in which the open state and the shielded state werealternately switched by controlling the opening degree of the pressurecontrol valve of the gas exhaust unit 50. In the simulation 2, the gainwas substantially not decreased even when the frequency was 0.1 kHz, anda gain of −20 db was obtained even when the frequency was 1 kHz. Thisshows that the pressure can be greatly increased/decreased at a highfrequency in the plasma processing apparatus 10.

Test Example 1 and Comparative Test Example 1

In a test example 3, N₂ gas of 500 sccm was supplied into the processingchamber 12 and the open state was switched to the shielded state by themovement of the second member 62 in the plasma processing apparatus 10including the first cylindrical part 61 a and the second cylindricalpart 62 a having the same sizes as those set in the simulation 1. Then,temporal changes of the pressure in the first space S1 were monitored.Further, a pressure increasing time in the first space S1 and a pressuresettling time in the first space S1 were obtained. The pressureincreasing time is a period of time between when the amount of increasein the pressure in the first space S1 from an initial pressure reaches10% of a pressure difference between the initial pressure and a targetpressure in the first space S1 and when the amount of increase in thepressure in the first space S1 reaches 90% of the pressure differencebetween the initial pressure and the target pressure. The pressuresettling time is a period of time between when the shielded state isformed and when the pressure in the first space S1 is substantially notchanged.

In the comparative test example 1, N₂ gas of 500 sccm was supplied intothe processing chamber 12 of a plasma processing apparatus differentfrom the plasma processing apparatus 10 of the test example 1 in thatthe baffle structure 60 had the baffle plate of the simulation 2, andthe open state was switched to the shielded state by controlling thepressure control valve of the gas exhaust unit 50. Then, temporalchanges of the pressure in the first space S1 were monitored. Further,the pressure increasing time in the first space S1 and the pressuresettling time in the first space S1 were obtained. In the comparativetest example 1, a state in which the opening degree of the pressurecontrol valve of the gas exhaust unit 50 was minimum was set to theshielded state, and a state in which the opening degree of the pressurecontrol valve of the gas exhaust unit 50 was maximum was set to the openstate.

FIG. 13 is a graph showing the results of the test example 1 and thecomparative test example 1. In FIG. 13 , the horizontal axis representstime and the vertical axis represents the pressure in the first spaceS1. In FIG. 13 , the temporal changes of the pressure in the first spaceS1 of the test example 1 and the temporal changes of the pressure in thefirst space S1 of the comparative test example 1 are illustrated. Asclearly can be seen from FIG. 13 , when the open state was switched tothe shielded state, the speed of the increase in the pressure in thefirst space S1 was higher and the pressure settling time in the shieldedstate was considerably shorter in the test example 1 than in thecomparative example 1. Specifically, the pressure settling time and thepressure increasing time of the comparative test example 1 were 13.5 secand 6.7 sec, respectively. The pressure settling time and the pressureincreasing time of the test example 1 were 4.6 sec and 2.3 sec,respectively.

Test Example 2 and Comparative Test Example 2

In a test example 2, N₂ gas of 500 sccm was supplied into the processingchamber 12 of the plasma processing apparatus same as that in the testexample 1, and the pressure in the first space S1 was changed by themovement of the second member 62 from 20 mTorr higher than the pressurein the first space S1 in the open state of the test example 1 to 120mTorr lower than the pressure in the first space S1 in the shieldedstate of the test example 1. Then, temporal changes of the pressure inthe first space S1 were monitored. Further, a pressure settling time inthe first space S1 and a pressure increasing time in the first space S1were obtained. The pressure increasing time is a period of time betweenwhen the amount of increase in the pressure in the first space S1 froman initial pressure reaches 10% of a pressure difference between theinitial pressure and a target pressure in the first space S1 and whenthe amount of increase in the pressure in the first space S1 reaches 90%of the pressure difference between the initial pressure and the targetpressure. The pressure settling time is a period of time between whenthe shielded state is formed and when the pressure in the first space S1is substantially not changed.

In the comparative test example 2, N₂ gas of 500 sccm was supplied intothe processing chamber 12 of the plasma processing apparatus same asthat in the comparative example 1, and the pressure in the first spaceS1 was changed from 20 mTorr to 120 mTorr by controlling the pressurecontrol valve of the gas exhaust unit 50. Then, temporal changes of thepressure in the first space S1 were monitored. Further, a pressuresettling time in the first space S1 and a pressure increasing time inthe first space S1 were obtained.

FIG. 14 shows the results of the test example 2 and the comparativeexample 2. In FIG. 14 , the horizontal axis represents time, and thevertical axis represents the pressure in the first space S1. In FIG. 14, temporal changes of the pressure in the first space S1 of the testexample 2 and temporal changes of the pressure in the first space S1 ofthe comparative example 2 are illustrated. As clearly can be seen fromFIG. 14 , the speed of the increase in the pressure in the first spaceS1 was higher and the time for the pressure in the first space S1 tosettle to 120 mTorr was shorter in the test example 2 than in thecomparative example 2. Specifically, the pressure settling time and thepressure increasing time of the comparative example 2 were 1.92 sec and1.09 sec, respectively. The pressure settling time and the pressureincreasing time of the test example 1 were 0.93 sec and 0.42 sec,respectively.

Test Example 3 and Comparative Example 3

In a test example 3, the same plasma processing apparatus as that in thetest example 1 was used, and the relation between the flow rate of N₂gas supplied into the processing chamber 12 and the pressure in thefirst space S1 in each of the open state and the shielded state wasobtained.

In the comparative example 3, the same plasma processing apparatus asthat in the comparative example 1 was used, and the relation between theflow rate of N₂ gas supplied into the processing chamber 12 and thepressure in the first space S1 in each of the open state and theshielded state was obtained.

FIG. 15 shows results of a test example 3 and a comparative example 3.In FIG. 15 , the horizontal axis represents a flow rate of N₂ gas andthe vertical axis represents a pressure in the first space S1. As shownin FIG. 15 , the relation between the flow rate of N₂ gas and thepressure in the first space S1 in the open state of the test example 3is substantially the same as that between the flow rate of N₂ gas andthe pressure in the first space S1 in the open state of the comparativeexample 3. This shows that the baffle structure 60 used in the testexample 3 can provide the same pressure controllability as that of thepressure control valve of the gas exhaust unit 50 in a low pressureregion. When the flow rate of N₂ gas is smaller than or equal to 500sccm, the relation between the flow rate of N₂ gas and the pressure inthe first space S1 in the shielded state of the test example 3 issubstantially the same as that between the flow rate of N₂ gas and thepressure in the first space S1 in the shielded state of the comparativeexample 3. When the flow rate of gas is greater than 500 sccm, thebaffle structure 60 used in the test example 3 can set the pressure inthe first space S1 to a higher level than that set by the pressurecontrol valve of the gas exhaust unit 50 used in the comparative example3 This shows that the pressure control valve of the gas exhaust unit 50can provide excellent pressure controllability in a high pressure rangein the case of using the baffle structure 60 of the test example 3.

DESCRIPTION OF REFERENCE NUMERALS

-   10: plasma processing apparatus-   12: processing chamber-   12 s: sidewall-   14: mounting table-   18: lower table-   20: electrostatic chuck-   20 r: mounting region-   30: upper electrode-   GS: gas supply unit-   50: gas exhaust unit-   60: baffle structure-   61: first member-   61 a: first cylindrical part-   61 h: through-hole-   62: second member-   62 a: second cylindrical part-   69: shaft body-   70: driving unit-   Cnt: control unit-   S1: first space-   S2: second space

What is claimed is:
 1. A substrate processing apparatus comprising: achamber having at least one gas inlet and at least one gas exhaust line,the chamber having an internal space; a mounting table disposed in thechamber; a baffle unit disposed so as to surround the mounting table,the baffle unit including: a first member separating the internal spaceof the chamber into a first space and a second space, the first spacecommunicating with the at least one gas inlet, the second spacecommunicating with the at least one gas exhaust line, the first memberhaving a first cylindrical portion, a lower annular portion and an upperannular portion, the lower annular portion extending from a lower end ofthe first cylindrical portion to the mounting table, the upper annularportion extending from an upper end of the first cylindrical portion toa sidewall of the chamber, the first cylindrical portion having aplurality of vertically elongated through holes arranged in acircumferential direction, the lower annular portion and the upperannular portion being imperforate; and a second member having a secondcylindrical portion disposed so as to surround the first cylindricalportion, an annular gap being formed between the first cylindricalportion and the second cylindrical portion in a plan view, the secondcylindrical portion having a vertical dimension greater than a verticaldimension of each of the vertically elongated through holes; and adriving unit configured to vertically move the second member between afirst position and a second position lower than the first position, theplurality of vertically elongated through holes being completely coveredby the second cylindrical portion in a lateral view and the first spacecommunicating with the second space via the vertically elongated throughholes and the annular gap when the second member is at the firstposition, wherein the second cylindrical portion has no through hole,wherein in the plan view, a width of the annular gap extends radiallyoutwardly from the first cylindrical portion to the second cylindricalportion when the second member is in the first position, and with thesecond member in the first position, a flow path flows: from the firstspace radially outwardly through each of the vertically elongatedthrough holes into the annular gap, then vertically downwardly throughthe annular gap, and then from the annular gap to the second space. 2.The substrate processing apparatus of claim 1, wherein the gap issubstantially 0.4 mm.
 3. The substrate processing apparatus of claim 1,wherein the second cylindrical portion is positioned below the pluralityof vertically elongated through holes when the second member is at thesecond position.
 4. The substrate processing apparatus of claim 1,wherein the second member has a second annular portion extending from alower end of the second cylindrical portion to outward, and a gap isformed between the second annular portion and the sidewall of thechamber.
 5. The substrate processing apparatus of claim 1, furthercomprising an exhaust unit connected to the at least one gas exhaustline.
 6. The substrate processing apparatus of claim 5, wherein theexhaust unit comprises a vacuum pump.
 7. The substrate processingapparatus of claim 1, wherein the sidewall of the chamber has an upperportion and a lower portion, and wherein the substrate processingapparatus further comprises an annular supporting member sandwichedbetween the upper portion and the lower portion and configured tosupport the first member.
 8. The substrate processing apparatus of claim1, wherein the plurality of vertically elongated through holes arearranged at a regular interval in a circumferential direction.
 9. Thesubstrate processing apparatus of claim 1, wherein each of the pluralityof vertically elongated through holes has a width equal to or less than3.5 mm.
 10. The substrate processing apparatus of claim 1, wherein eachof the plurality of vertically elongated through holes has a verticaldimension of substantially 30 mm.
 11. The substrate processing apparatusof claim 1, wherein the second cylindrical portion has a thickness ofsubstantially 5 mm.
 12. The substrate processing apparatus of claim 1,wherein the second member has a second annular portion extendingdiametrically outward direction from a lower end of the secondcylindrical portion below a location at which the upper annular portionof the first member is supported by the sidewall of the chamber suchthat, when the second cylindrical portion is in a vertical position inwhich the second cylindrical portion does not face the through holes ofthe first cylindrical portion, the first space communicates with thesecond space through the through holes of the first cylindrical portionand between the sidewall of the chamber and the second annular portionextending from the lower end of the second cylindrical portion.
 13. Thesubstrate processing apparatus of claim 1, wherein the second member hasa second annular portion extending from a lower end of the secondcylindrical portion to outward, and a gap is formed between the secondannular portion and the sidewall of the chamber; and the substrateprocessing apparatus further comprises one or more shaft bodiesextending in a vertical direction through the second annular portion andat least one of the shaft bodies being connected to the driving unit.